Roach explained that foot stomps typically happen in a match between a southpaw and an orthodox fighter.

"When you have a lefty [Pacquiao] fighting a right-hander [Marquez]," Roach told LA Times' Bill Dwyre, "you have guys stepping on each other's lead foot more than righty-righty or lefty-lefty.

He said that sometimes, it is used as a boxing trick to stop a boxer in his tracks during a fight.

In the third fight between Pacquiao and Marquez in November 2011, the Mexican was seen stepping on Pacquiao’s foot at least five times.

“It had happened a lot in their other fights, and even could be used as a strategy by Marquez [so we asked] the referee to come to our dressing room before the [fourth] fight so we could warn him to watch for that," said Roach.

However, he said the unexpected happened in the fourth fight last December.

Roach said he realized, after reviewing the overhead camera shots of the fourth fight, that it was Pacquiao who accidentally stepped on Marquez’s foot moments before the Filipino got knocked out.